Comparison of Hydrocarbons Extracted from Seven Coals by Capillary

9

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on July 15, 2016 | http://pubs.acs.org Publication Date: September 10, 1984 | doi: 10.1021/bk-1984-0264.ch009

Comparison of Hydrocarbons Extracted from Seven Coals by Capillary Gas Chromatography and Gas Chromatography-Mass Spectrometry SYLVIA A. FARNUM, RONALD C. TIMPE, DAVID J. MILLER, and BRUCE W. FARNUM Energy Research Center, University of North Dakota, Grand Forks, ND 58202 Seven coals ranging in rank from lignite to bituminous were solvent-extracted with chloroform. The hexane-soluble portions of the extract were analyzed by capillary GC and GC/MS. Selected ion profiles (mass chromatograms) derived from the total ion data were prepared. The coal extract profiles f e l l into four groups: 1) Big Brown 1, Big Brown 2 (Texas lignites) and Morwell (Australian brown coal); 2) Beulah 3 (North Dakota lignite) and Wyodak (Wyoming, subbituminous); 3) Highvale (Alberta, subbituminous); and 4) Powhatan (Ohio, bituminous). Several groups of hydrocarbon biological markers were identified in the coal extracts including n-alkanes, pristane, sesquiterpenes, several tricyclic alkanes and pentacyclic triterpanes with molecular weights from 398 to 454. The n-alkanes recovered by extraction amount to less than 10% of those produced during liquefaction indicating that bond-breaking reactions during liquefaction lead to the formation of n-alkanes. Coals have been shown to contain paraffinic hydrocarbons whose structures arise directly from biological precursors Q , 2). The types of hydrocarbons usually considered in this group of biological markers include n-alkanes, acyclic isoprenoids, steranes and terpanes. The amounts of these materials that can be extracted from coal are small but even the characterization of these small amounts of alkanes can be very important in determining the origin and maturity of coals. A detailed understanding of the origin of coals and of the diagenesis and maturation of coals may someday be deduced by drawing upon the large body of available information on the relationships of biological markers to the geologic history of rocks, sediments, o i l shales and petroleum. The subject has been reviewed (1,2). Some biological markers have also been detected in coal liquefaction products (3,4). Experimental Seven coals were selected for analysis in this study. These seven coals have also been utilized for various liquefaction studies at the University of North Dakota Energy Research Center (UNDERC). Their proximate and ultimate analyses are shown in Table I. 0097-6156/84/0264-0145$06.00/0 © 1984 American Chemical Society Schobert; The Chemistry of Low-Rank Coals ACS Symposium Series; American Chemical Society: Washington, DC, 1984.

146

T H E CHEMISTRY OF LOW-RANK COALS

CO 4->

Ο

Ο r— r H r H ο Γ— 00 eu ccj


Ή

70% of alkanes formed from pyrolysis of Australian brown coal were non-extractable (7). Table IV. Coal B3 MOC BB1 BB2 WY01 ALB1 P0W1

Extracted/Separated n-Alkanes (Wt % maf Coal) Hexane Soluble CHC1 Extract 3

0.15 ND ND ND 0.20 0.025 0.022

Liquefaction Product After 13 Recycle Passes 1.7 NA 3.8 NA 1.7 NA 0.96

ND = Not Detected NA = Comparable values not available

Schobert; The Chemistry of Low-Rank Coals ACS Symposium Series; American Chemical Society: Washington, DC, 1984.

15

Comparison of Hydrocarbon Extractions

F A R N U M ET AL.


0.3

3.0

Wt.%0.2 Product

•

/CPI=0.99

>JU

2.0 Wt.% Extr.

C P I = 1.8

0.1

/

10

/

14

18

k

\ /

22

26

30

*

34

1.0

36

No. of Carbons Figure A,

2.

C o m p a r i s o n on

and n - a l k a n e

(Beulah

lignite

n-alkane

distribution feed

from

distribution CPU b o t t o m s

from Beulah recycle

lignite,

product,

•

coal).

No. of C a r b o n s 3.

Figure

Comparison of

subbituminous recycle

coal,

product,

·

O,

n-alkane

and

(Wyodak

extract

n-alkane

distribution

distribution

subbituminous

for

Wyodak

f r o m CPU b o t t o m s

coal).



152

T H E CHEMISTRY OF LOW-RANK COALS

10

14

18

22

26

30

34

36

No. of Carbons Figure

4.

Powhatan

Comparison of bituminous

CPU b o t t o m s

recycle

n-alkane

coal, Δ , product

and

extract

distribution

for

n-alkane

distribution

from

(Powhatan

bituminous

feed

coal)


A.

9.

FARNUM ET AL.

Comparison of Hydrocarbon Extractions

153


The CHX extracts from B3 and P0W1 were the only extracts of the seven that contained pristane. The bituminous coal, P0W1, extract had more pristane than the B3 extract, Table III. Phytane was not detected in any of the extracts, although both pristane and phytane were found in a l l of the coal liquefaction products from B3, BB1, WY01, and P0W1. The ratio of pristane to phytane was about 5:1. It has been reported that the pristane content of the saturated hydrocarbon fraction from subbituminous coals of more than 76% C begins to increase (1). The increase in phytane begins roughly at 83-85% C. Cyclic Hydrocarbons. Some of the cyclic hydrocarbons found in the CHX coal extracts are shown in Table V. They were tentatively identified by capillary GC/MS except for the naphthalenes, for which authentic standards were available. Selected ion profiles were used to detect sesquiterpenes (m/e 206, 191), sesquiterpanes (m/e 208), alkanes (m/e 141), alkyl benzenes (m/e 191, 163), steranes (m/e 217), and tricyclic terpenoids (m/e 191, 163) as well as the m/e values for the parent ion of specific compounds. Figure 5 shows the results O f one of these selected ion profiles at m/e 206, from the CHX extract of WY01 along with a portion of the total ion chromatogram. The peaks shown in the m/e 206 trace between scan numbers 240 and 300 correspond to the sesquiterpenes listed in Table V. A l l of these compounds showed M-15 peaks of various intensities (m/e 191), relatively intense M-29 peaks (m/e 177) and m/e 121 peaks. One compound, c, had a prominent even mass peak at 178. Six had more prominent M-43 (m/e 163) peaks than the others. The fragmentation patterns shown by these C H 6 sesquiterpenes resemble those reported by Richardson (8) for a series of C H 8 bicyclics identified in a crude oil. We tentatively assigned a C-10 bicyclic structure with one double bond and varying alkyl substituents in accord with the observed fragmentation patterns. Baset et a l . assigned similar structures to nine m/e 206 compounds they observed in Wyodak extracts (6). Gallegos (9) also found a number of sesquiterpenes (m/e 206, 191) in pyrolysis products of six coals including Wyodak subbituminous coal and Noonan North Dakota lignite. The sesquiterpene distribution for the CHX extracts of B3 and WY01 were distinctive and similar. The distribution for ALB1 gave smaller concentrations of sesquiterpenes, Table V, but the mass spectra were identical for comparable ALB1, WY01, and B3 sesquiterpenes with the same GC retention times. P0W1, MOC, BB1, and BB2 CHX extracts did not contain these compounds. No sesquiterpanes with (m/e 208) were detected in any of the CHX extracts. Gallegos also detected cadalene (m/e 198, 183) in some of the coal pyrolysis products he investigated (9). Cadalene was present in the ALB1 extract and was probably a small component in the B3 extract. It was not found in the extracts of the other coals. Another compound which gave identical mass spectra in two of the extracts, WY01 and ALB1, appears to be one of the tricyclic alkanes, m/e = 276. An intense peak at m/e 247 corresponds to M-29. The mass spectrum was an excellent match with that presented by Philip, et a l . (10) for which the structure shown below was proposed. An intense peak at m/e 123 was noted and is probably due to the fragmentation shown. 15

2

15

2



2

11

11

11

11

h

30 52

h

31 54

h

31 54

h

32 56

h

33 58

c

c

c

c

c

h

29 50

?

30

c

17

C H

tricyclic alkene

C20H36 tricyclic alkane

15

Alicyclic terpenoids: C H 6 sesquiterpene

Miscellaneous : naphthalene 2-methylnaphthalene 1-methylnaphthalene C2-naphthalene cadalene

a b c d e f g h

.7 .8 .8 .9 .2 .0 .9 .2 .3 .4 .4 .5 .6 .2 .0 .8 .0 .7

230 233 236 272 284 285 287 295 312 321

.9 .0 .6 .3 .4

100 104 106 108 111 113 114 116

47 72 75 95 160

276 252 234 Not Shown 298 412 426 426 440 454

206 206 206 206 206 206 206 206

198

Ion

0 .07

1 .2

1 .7

2 .3 0 10

1 9 1 12 0 24

0 .31

B3

0.29 0.10

0.32 0.29 0.04

MOC

3.0 1.7

1.1 3.5

3.3

0.66

8 0 2 3 3 6 5 96

1 .0

0 96

2 1 13 3 8 4 1 0

0 18 0 19 0 09

Capillary GC, Area WY01 BB1 BB2

Other Hydrocarbons Found in Extracts of Coal, Capillary GC and GC/MS, Area %, FID

Retention Time, Min.

Table V.


17 27 9 17

0 27

0 46 0 50 0 10

0 0 1 0

0 70

1 3

0 12 0 38 0 13

ALB1

0.03

0.13 0.13

0.10

1.2 2.7 2.0 0.68 1.3

P0W1

9

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r Ο

τη

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τα ·

Comparison of Hydrocarbons Extracted from Seven Coals by Capillary

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